1. Field of the Invention
This invention relates to a lock and is particularly though not solely for use to provide a security chain for doors or windows, or which is usable in other circumstances.
2. Description of the Prior Art
Locks of the security chain or night latch type currently available usually comprise a member with a keyhole slot fixed to a door or door jamb into which is insertable a member fixed on a chain attached to the other of the door or door jamb. Such chains have disadvantages in that they are often cumbersome and unattractive in appearance and the strength of the construction can be suspect, the material about the keyhole slot being inclined to distort under pressure to allow the slotted member to spring from the slot. Also pressure on fixing screws can have a substantial component along the screw. Furthermore such devices present members which stand out from the door and door jamb which is undesirable. They also require an operator to insert the member into the keyhole slot.